A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis

Abstract

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from stellar coronae, and they are always accompanied by flares. In this study, we present high-resolution spectroscopic observations of a long-duration optical flare on the RS CVn-type star UX Arietis (UX Ari). Around the flare peak, we have detected a far-blueshifted emission component in the H$α$ line profile---a signature of an erupting prominence---indicating a possible stellar CME. After correcting for projection effects, the eruption velocity reaches $\sim -432$ km s$^{-1}$ when assuming radial propagation, significantly exceeding the escape velocity of the primary component ($\approx 304$ km s$^{-1}$). This strongly supports the detection of a stellar CME. The mass of this CME is at least $2.7 \times 10^{20}$ g, and its kinetic energy is $2.5 \times 10^{35}$ erg. The mass value is consistent with the solar flare--CME scaling relation, while its kinetic energy lies below the solar trend. The flare itself released an energy of $4.2 \times 10^{36}$ erg in the H$α$, corresponding to a white-light bolometric energy of roughly $2.8 \times 10^{38}$ erg. Throughout the flaring event, evolving asymmetries in the H$α$ profile reveal complex plasma dynamics.